Siemens SINUMERIK 840C - Manual (Page 1125)

12 Functional Descriptions 08.96
12.33.5 Speed setpoint filter
1
k
vmax
=
2(T
ers,n
+ T
n,w,gl
+ T
tot,LR
+ T
abt,LR
)
T
ers,n
= Equivalent time of closed speed control loop
T
n,w,gl
= Equivalent time of speed setpoint filter
T
tot,LR
= Deadtime position/speed control loop (1 x T
LR
)
T
abt,LR
= Sampling of position actual value (0.5 x T
LR
)
LR = Position controller
Another application for the low-pass function as a speed setpoint filter is the interpolation of
speed setpoint steps. The speed setpoints are output by the NC in the position controller clock
cycle. This can be set to a much higher value than the speed controller clock cycle.
Note
Speed setpoint filters can be used in interpolating axis groupings to compensate the different
dynamic responses in the speed control loops of individual axes.
The total equivalent time constant (= equivalent time constant of speed control loop +
equivalent time constant of speed setpoint filter) must be set such that it is the same for all
mutually interpolating axes.
The input of damping values close the minimum input limit causes overshoots in the time
range up to a factor of 2. This effect is raised to a power in the case of 2 configured low-
pass filters with the same setting parameters. These filters still have a linear response in low-
level signal operation. In high-level signal operation, the filter states may be limited in some
cases by the maximum numerical formats (as defined by the processor register width). The
filter characteristic becomes non-linear for a brief period. Overshoots or unstable reactions do
not occur.
12–350 © Siemens AG 1992 All Rights Reserved 6FC5197- AA50
SINUMERIK 840C (IA)